1. Field of the Invention
The present invention relates generally to medical devices, and, in particular, to a system of improved irrigation and aspiration catheters used in the containment and removal of emboli resulting from therapeutic treatment of occlusions within blood vessels.
2. Description of Related Art
Human blood vessels often become occluded or blocked by plaque, thrombi, other deposits, or emboli which reduce the blood carrying capacity of the vessel. Should the blockage occur at a critical place in the circulatory system, serious and permanent injury, and even death, can occur. To prevent this, some form of medical intervention is usually performed when significant occlusion is detected.
Balloon angioplasty, and other transluminal medical treatments, are well-known, and have been proven efficacious in the treatment of stenotic lesions in blood vessels. The application of such medical procedure to certain blood vessels, however, has been limited, due to the risks associated with creation of emboli during the procedure. For example, angioplasty is not the currently preferred treatment for lesions in the carotid artery, because of the possibility of dislodging plaque from the lesion, which can enter the various arterial vessels of the brain and cause permanent brain damage. Instead, surgical procedures such as carotid endarterectomy are currently used, wherein the artery is split open and the blockage removed, but these procedures present substantial risks.
Other types of intervention for blocked vessels include atherectomy, deployment of stents, introduction of specific medication by infusion, and bypass surgery. Each of these methods are not without the risk of embolism caused by the dislodgement of the blocking material which then moves downstream. In addition, the size of the vessel may limit access to the vessel.
Thus, there is a need for a system to contain and remove such emboli. Various devices and methods have been proposed, but none have been especially commercially successful. Perhaps this is because a number of significant problems are faced in designing a system which will quickly and easily, yet effectively, evacuate emboli from a treatment location within a blood vessel. First, the small size of certain vessels in which such therapy occurs is a limiting factor in the design of emboli containment and removal systems. Vessels as small as 3 mm in diameter are quite commonly found in the coronary arteries, and even certain saphenous vein graph bypass vessels can also be as small as 3 mm or 4 mm; although some can range as high as 7 mm. Certain of the carotid arteries also can be as small as 4 mm in diameter; although, again, others are larger. Nevertheless, a successful emboli removal system must be effective within extremely small working areas. The system is equally effective in larger vessels, those of 5 mm or more in diameter.
Another obstacle is the wide variety in emboli dimensions. Although definitive studies are not available, it is believed that emboli may have approximate diameters ranging anywhere from tens of micrometers to a few hundred micrometers. More specifically, emboli which are considered dangerous to the patient may have diameters as large as 200 to 300 micrometers or even larger. Thus, an effective emboli removal system must be able to accommodate relatively large embolic particles and, at the same time, fit within relatively small vessels.
Another difficulty that must be overcome is the limited amount of time available to perform the emboli removal procedure. That is, it will be understood that in order to contain the emboli produced as a result of intravascular therapy, the vessel must be occluded, meaning that no blood perfuses through the vessel to the end organs. Although certain perfusion systems may exist or may be developed which would provide occlusion to emboli while permitting the substantial flow of blood, at present, the emboli may be contained only with a complete occlusion as to both blood flow and emboli escapement. Thus, again depending upon the end organ, the complete procedure, including time for the therapeutic treatment as well as exchanges of angioplastic balloons, stents, and the like, must be completed within just a few minutes. Thus, it would be difficult to include time for emboli removal as well. This is particularly true in the larger size vessels discussed above wherein a larger volume results in additional time required for emboli evacuation.
Moreover, it is important that an emboli containment and removal system be easy to use by physicians, and compatible with present therapeutic devices and methods. In addition, there are other difficulties which have made the successful commercialization of emboli containment and removal systems thus far virtually unobtainable.